Board Thread:General Discussion/@comment-29907776-20180617022636/@comment-6769189-20180629060737

To my understanding the demons he sealed in Temi-Ni-Gru were meant to be deterents, at least for humans. They are referred to as Gatekeepers.

As for Mundus, it is entirely possible that even though Sparda was strong enough to win the fight, he wasnt strong enough to go for the kill, which is why Mundus needed to be sealed. I feel like Sparda's power escalation would be much like Dante's in DMC3, where as Sparda makes his way to Mundus, he becomes strong enough to match him.